Grinding machine



April 26, 1955 E. v. FLANDERfs rs1-AL 2,706,872

GRINDING MACHINE Filed June 1, 195s :s sheets-sheet 1 w "Sk APIX 26,1955 E. v. FLANDERS Erm.

GRINDING MACHINE 3 Sheets-Sheet 2 Filed' June 1, 1953 W50 Maw/7&2

GRINDING MACHINE 3 vSheets-Sheet 3 Filed June l, 1953 mln" lmm QW Q m mQ m L- m Q Q n Q l@ .vm f n N@ m w n VNU. n ,mf m

United States Patent O GRINDING MACHINE Ernest V. Flanders and CarrollH. Drury, Springfield, Vt., assignors to `Tones & Lamson MachineCompany, a corporation of Vermont Application June 1, 1953, Serial No.358,862

Claims. (Cl. 51--95) This invention relates primarily to machines forgrinding relief in the threads of taps, but embodies principles whichcan be used in machines for grinding relief on reamers, milling cuttersand other tools. For simplicity the description will be restricted to athread grinder for taps. It is known that the threads on the lands of atap should be relieved in a radial direction so that there will be norubbing on the work back of the cutting edges. To accomplish this it hasbeen the practice to move the grinding wheel toward and from the workpiece as many times during a revolution of the latter as there areflutes on the tap, or to mount the work supporting spindle in a carriagewhich was given a similar movement toward the grinding wheel. This is apractical construction where the taps are large in diameter and thespeed of rotation of the work piece is therefore not very high. It hasproved quite impractical, however, in the grinding of taps of smallsize, say one-half inch in diameter or less, as these must be rotated athigh speeds to get the volume of production necessary to maintain acompetitive cost. It has become the custom, therefore, to grind thesesmall taps with no relief whatever.

It is a major object of our invention to provide novel means whereby thework is oscillated toward and away from the grinding wheel, but theamount of weight which has to be oscillated in the combination of thework itself and the work supports has been reduced to practically zero,so that the speed of rotation in the grinding from the solid of threadswith relief on a guarter inch tap, for example, can be increased from100 R. P. M. on former machines to at least 600 R. P. M. in machinesconstructed in accordance with the present invention. This makes itperfectly practical to grind and relieve the threads of small taps on anormal production basis, thus making superior free cutting taps at lowcost. Briefly, this is accomplished by mounting within the work-drivingspindle a coaxial shaft which has a tapered hole supporting theheadstock center on which the work is mounted. Opposite the headstock isa tailstock having a similar center supporting shaft, with, of course,no surrounding spindle. The two shafts are driven at a higher speed thanthe spindle, being two, three or four times as fast depending on thenumber of lutes on the tap. The worksupporting centers are made withtheir points eccentric to the axis of rotation, and preferably with acounterweight ground into the part between the point and the tapershank, so that the combined counter-weighting of the two centers willcompensate not only for the offbalance of the eccentric points but forthe off-center weight of the tap itself.

The invention will now be more completely described, as well as themanner in which the above objects are achieved, with reference to theaccompanying drawings, in which:

Fig. 1 is a front view of a portion of a thread grinding machine inwhich our invention is embodied;

Fig. 2 is a section on line 2 2 of Fig. l;

Fig. 3 is a view, on an enlarged scale and with eccentricitiesexaggerated, of one of the work supporting centers;

Fig. 4 is a development, or stretch-out, view of the headstock andtailstock with the associated gearing;

Fig. 5 is a diagrammatic view showing the relation between the workpiece, its axes of rotation, and the grinding wheel at the beginning ofthe grinding of a thread on one of the lands of a tap; and

ice

Fig. 6 is a similar View showing the land about to pass out of contactwith the grinding wheel;

Figs. 7 through 10 are views of a modification of the gearingarrangement of Fig. 4 for purposes to be described.

The headstock 10 and the tailstock 11 are mounted on a suitable basecontaining driving mechanism, coolant and lubricant reservoirs, andvarious other parts which are not important here and which willtherefore not be described. Such a machine may be as described in U. S.,l Patent 2,184,011 issued December 19, 1939, to R. E. t

Flanders. A grinding wheel 13, mounted in a housing 14, is driven,dressed, and fed radially by mechanism which may be standard as far asthe present improvements are concerned. If there is a helical thread tobe cut there must, of course, be a steady longitudinal feed between thewheel and the work. If, on the other hand, the grooves to be cut areannular' as in a hob with no lead, an intermittent longitudinal feed isrequired. The present invention is usable with either type of feed, andsince they are well known in the art, they need not be referred to indetail here.

Within the headstock is a spindle 15 mounted in ball bearings 16. Withinthe spindle is a center supporting shaft 17 mounted on bearings 13between it and the spindle. In the tailstock 11 is a center supportingshaft 19 mounted on bearings 20. The two shafts 17 and 19 are drivenfrom a shaft 21, mounted in the frame in bearings 22, by pairs of gears23, 24 and 25, 26, each having a two to one ratio. Thus the shafts 17and 19 rotate at all times in synchronism and in a definite angularrelation; and, as will be seen, with the center supporting shaftsrotating at a speed which is an integral multiple of that of thespindle.

The shaft 21, which drives both the spindle and the center supportingshafts, is itself driven from a shaft 27 having a worm gear 28 engagingthe main drive worm 29. Between shafts 21 and 27 is a change speedmechanism consisting of two cluster gears 30 and 31, the latter of whichis keyed so as to slide on shaft 21, while the cluster gear 30 is xed onshaft 27. The cluster gear 30 has a gear 33 meshing with a gear of thesame size 34 fixed on the spindle. Since Fig. 2 is made as a developedor stretched-out view for clarity, as otherwise some gears would behidden behind others, it happens that gears 33 and 34 are not shown asbeing in mesh except by the conventional device of joining them bydotted lines. This is much clearer than showing the gears in theirgeometrically true positions with some partially tucked away behindothers. It will be understood, however, that gears 33 and 34 areactually in mesh at all times, and that through them the spindle 15 isdriven at the same speed as shaft 27.

The function of the other gears in the clusters can now be considered.Gear 3S in the cluster 30 can be made to mesh with a gear 36 in thecluster 31 having half as many teeth. Since the spindle is driven at thesame speed as shaft 27 and the center supporting shaft 17 is driven bygears 23, 24 at twice the speed of shaft 21, this combination drives thecenter supporting shafts at a speed equal to 2X2 or four times the speedof the spindle. This is the condition desired for a tap with fourllutes. For a tap with three flutes a gear 38 on cluster 31 is shiftedto engage a gear 37 on cluster 30 having 2/3 as many teeth. This drivesthe center supporting shaft 17 at 2X3/2 or three times the speed of thespindle. When a gear 39 on the cluster 30 is in mesh with an equal gear40 on the cluster 31 the center supporting shaft rotates twice as fastas the spindle,'which is suitable for a tap with two flutes.

The center supporting shaft 17 (which is always synchronous and inangular alignment with the center carrying shaft 19 as pointed outabove) and the spindle 15 are coaxial; the oscillation of the worknecessary to cause the cutting teeth to be relieved is done solely bythe work supporting centers. One of these is shown in Fig. 3 on anenlarged scale and with the eccentricities greatly exaggerated, as canbe seen from the fact that the actual eccentricity of the conical pointwith respect to the axis of the center carrying shaft is radially about0.004". Since this would be invisible on the drawing it has been can beentirely eliminated.

magnified many times. The center 41 has the usual taper shank 42 fittinginto the tapered socket 43, but in the present case has a keyway 44engaging a key 4S in the socket to preserve the correct angularorientation and to ensure that the two centers will have theireccentricities lying in the same direction.

The tapered shank 42 has a center line at 42a and is joined by a reducedportion 46 with an eccentric cylindrical portion 47 having its centerline at 47a. The center 41 terminates in a cone 43, having its centerline at 48a and, which aside from this center line offset, is like theusual lathe or grinder center. it will be plain that as the centerrotates about its axis 42a, the cylindrical portion 47 will also rotateabout it, but with its own axis displaced as shown in Fig. 3. Likewisethe conical point 4S will rotate about the axis 42a but with its ownaxis 48a displaced, in a direction exactly opposite to the axis 47a. Thetwo centers shown in Fig. l have their respective axes in line7 andsince the work piece 52 to be ground is supported on the conical points48 (though rotated with the spindle by a dog to be described) itexecutes an orbital motion around the spindle axis.

This orbital rotation is more rapid than the rotation of the spindle,being a multiple of it corresponding to the number of flutes 53 on thetap being ground. For a two ute tap the orbital speed will be twice thatof the spindle, for a three flute tap three times, and for a four iiutetap four times. The way in which the difference in relative speeds ismade possible by the cluster gears has been described above. The orbitalmotion, as will be seen from Figs. and 6, acts to displace the workpiece gradually toward the grinding wheel during the period when one ofthe lands is being ground, or rather when threads are being ground on itsince the threads will in general be ground completely, with reliefincluded, from a cylindrical but fluted tap blank.

The operation of the orbitally moving centers in securing the desiredrelief has been shown diagrammatically in Figs. 5 and 6, which forsimplicity and for the purpose of showing the versatility of theinvention omit any idea of threads. In the first of these figures thegrinding wheel is just making contact with one land of the tap or otherworkpiece and the axis 48a which is the axis of the conical point 48 andtherefore also the axis of the tap itself, is on the side of the axis42a of the spindle remote from the grinding Wheel. ln Fig. 6 thespindle, and therefore the tap which is dog-coupled to it, has movedthrough an angle X suicient to bring the heel 55 of the land against thegrinding wheel. During this time the axis 48a of the tap has movedthrough an angle 4X around the axis 42a of the spindle, thus crowdingthe land 54 gradually, but at an accelerating rate, into the grindingwheel. The rst part of the grinding of the land is substantiallyconcentric, while the remainder becomes more and more eccentric. Therelation between the concentric and eccentric portions can be changed asdesired by varying the placement of angle X either by the setting of theworkholding dog 58 or by the location of the keyway 44, the relativepositions of the axes 42a and 48a at the time the land first makescontact with the wheel. lt should be realized that in the position ofthe axes in Fig. 5 their relative circular motion produces much lesschange in the eccentricity of the grind than the same relative motiondoes in the position of Fig. 6. The axis 48a which has completed only aportion of its rotation about axis 42a in Fig. 6, will complete itsrotation to the position of Fig. 5 while the flute is passing thegrinding wheel.

The function of the cylindrical but eccentric portion 47 of the center4l can now be considered. If this were coaxial with the axis 49 of thespindle there would be an unbalanced force developed by the orbitalmotion of the tap around the axis 42a as well as by the orbital motionof the conical point 48 around the same axis. This unbalance would tendto create vibration which, though slight, would adversely affect thefinish produced on the work. To avoid this the rotative speed of thework would have to be kept down. Even so the permissible speed would bemuch higher than in prior constructions in which either the entirespindle or the grinding wheel were bodily oscillated, but by propercorrelation of the eccentricity of the cylindrical portion 47 with theunbalance of the conical tips and the work piece, unbalance While thismay require ih center to be made especially for a particular size andweight of work piece, this is entirely feasible in production work, forthe centers are relatively inexpensive. Due to the identity andalignment of the two centers 41, the whole rotating mechanism, includingthe work piece, will be in complete dynamic balance.

Fig. 2 shows one arrangement for driving the work piece S2 from thespindle. The spindle has the usual face plate 56 which is here providedwith two pins 57 between which lits the tail of the usual dog 58. itwill be apparent that the slight angular and radial motion which theoribital motion will give to the dog can readily be accommodated by thepins without disturbing the driving action of the dog.

The arrangement described above will grind a relief on taps or reamershaving straight flutes, but both taps and reamcrs are also made withhelical utes and it is desirable that the grinder should be able tohandle either style. We provide novel arrangements for making themachine adaptable to helical as well as straight flutes. The fundamentalprinciple underlying this form of our invention is that the centersupporting shafts 17 and 19 are given, in addition to the rotationcorresponding to the number of utes as described above, an angulardisplacement relative to the spindle corresponding to the position 0fthe grinding wheel longitudinally of the work piece. This rotativedisplacement causes the position of a land relative to the grindingwheel to be the same all the way along the work piece being ground.

Figs. 7 through l0 show one form of device which is adapted for grindinghelical as well as straight tinted tools. The basic mechanism is thesame as that previously described, and has been designated by the samereference characters. The distinctive feature of the present form is inthe connection between the shaft 27 and the shaft 2i which drives bothcenter supporting shafts through pairs of gears 23, 24 and 25, 26. Shaft21a is keyed to a bevel gear 59, while gear 23 is driven by a gear 60 ofthe same diameter keyed to the hub 6l of a second bevel gear 62. Thegears 59 and 61 are coupled by bevel pinions 63 rotatable on studs 64carried by the hub 66 of a ring gear 67. This ring gear meshes with arack 68 guided in the headstock casting wall as shown in Figure 8actuated as will be described. if the rack is not moved the operationwill be the same as that described in the original form. However, if therack is moved at a rate related to the rate of traverse of the grindingwheel along the longitudinal axis of the work, the center carryingshafts will be displaced pro gressively by an amount in addition to theintegers of clusters 30 and 3l so that they will make the same shiftwith respect to the lands in all positions of the wheel, even though theflutes and lands in the work blank are helical.

To accomplish this we provide an adjustable cam 69 in which rides aroller 70 secured to the end of rack 68. The cam 69 is fastened to thestationary portion of the machine bed, while the rack and associatedmechanism move with the longitudinal traverse of the work past thegrinding wheel. It should be understood that this provides for movementof the rack a certain distance for a given longitudinal movement ofwheel relative to work. This can be done by mechanical means whether thework moves, as in the Flanders type of machine referred to, or in othertypes of machines in which the wheel head is moved along the work.

The ratio of rack movement to work-wheel movement is, of course,determined by the setting of the cam 69 along the graduated scale 7l.The cam is pivoted on the stud 72, and may be locked in the desiredposition by the locking nut 7 3. By proper selection of gear ratios inthe differential and between the rack and gear 67, the scale 7i may becalibrated directly in degrees of flute angle on the work blank.

By setting the cam to zero on scale 71, no correction will be fed intothe differential and the machine will relieve lands formed parallel tothe work axis.

From the foregoing description it will be apparent that we havedisclosed a grinding machine mechanism adapted to solve long standingproblems in the tool grinding field. Our invention has been found to beparticularly advantageous in the grinding of taps, reamers, hobs,milling cutters and the like where heretofore full relief grinding hasbeen inconsistent with high production and consequent 10W cost.Variations and modifications within the spirit of this invention mayoccur to persons skilled in the art to which it pertains. Therefore, theforegoing specification is presented by way of description and examplerather than by way of limitation.

We claim:

1. In combination, a machine bed, a headstock on said bed, a hollowspindle rotatably mounted thereon, a shaft journaled in said spindle andadapted to carry a work engaging center, means for rotating said spindleat a denite speed, a tailstock on said bed, a shaft journaled on saidtailstock and adapted to carry a work engaging center, centers carriedby both said shafts, said centers having work engaging portions, theaxes of which are offset from the axes of said shafts and means forrotating said shafts together at a speed other than the speed of saidspindle.

2. In combination, a machine bed, a headstock on said bed, a hollowspindle rotatably mounted thereon, a shaft journaled in said spindle andadapted to carry a work engaging center, means for rotating said spindleat a definite speed, a tailstock on said bed, a shaft journaled on saidtailstock and adapted to carry a work engaging center, centers carriedby both said shafts, said centers having work engaging cones, the axesof which are parallel to but no collinear with the axes of said shaftsand means for rotating said shafts together at a speed which is aselected multiple of the speed of said spindle.

3. In combination, a machine bed, a headstock on said bed, a hollowspindle rotatably mounted thereon, a shaft journaled in said spindle andadapted to carry a work vengaging center, means for rotating saidspindle at a definite speed, a tailstock on said bed, a shaft journaledon said tailstock and adapted to carry a work engaging center, centerscarried by both said shafts, said centers having work engaging cones theaxes of which are parallel to but not collinear with the axes of saidshafts and means for rotating said shafts together at a speed which is aselected integer multiple of the speed of said spindle.

4. In combination, a machine bed, a headstock on said bed, a hollowspindle rotatably mounted thereon, a shaft journaled in said spindle andadapted to carry work engaging center, means for rotating said spindleat a definite speed, a tailstock on said bed, a shaft journaled on saidtailstock and adapted to carry a work engaging center, centers carriedby both said shafts, said centers having work engaging cones the axes ofwhich are parallel to but not collinear with the axes of said shaftmeans for rotating said shafts together at a speed which is a selectedbut not collinear with the axes of said shafts, means for moving saidheadstock and tailstock together axially along said bed, and means foradding to the integer multiple speed a preselected factor as theheadstock and tailstock move axially.

5. In combination, a machine bed, a headstock on said bed, a hollowspindle rotatably mounted thereon, a shaft journaled in said spindle andadapted to carry a work engaging center, means for rotating said spindleat a denite speed, a tailstock on said bed, a shaft journaled on saidtailstock and adapted to carry a work engaging center, centers carriedby both said shafts, said centers having work engaging cones the axes ofwhich are parallel to but not collinear with the axes of said shafts,means for rotating said shafts together at a speed which is a selectedinteger multiple of the speed of said spindle, a cutting tool adapted toengage Work mounted between said centers, means for producing relativemotion between said tool and the work axially along said bed, and means'for adding to the rotation of said shafts a factor produced by saidrelative motion.

References Cited in the tile of this patent UNITED STATES PATENTS1,100,265 Smith June 16, 1914 1,239,268 Hammon Sept. 4, 1917 1,297,396Olson Mar. 18, 1919 1,365,337 Muller Jan. 11, 1921 1,478,433 Harris Dec.25, 1923 1,739,753 Flanders Dec. 17, 1929 2,209,228 Judge July 23, 19402,401,561 Gruenberg June 4, 1946

